#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n, m, x, y, sol, nr, fr[100010], Inapoi[100010];
vector < int > V[100010], VT[100010];
vector < vector < int > > S;

inline void DFST(int k)
{
    vector < int > :: iterator it;
    S[S.size() - 1].push_back(k);
    fr[k] = 0;
    for (it = VT[k].begin(); it != VT[k].end(); it++)
        if (fr[*it]) DFST(*it);
}

inline void DFS(int k)
{
    vector < int > :: iterator it;
    fr[k] = 1;
    for (it = V[k].begin(); it != V[k].end(); it++)
        if (!fr[*it]) DFS(*it);
    Inapoi[++nr] = k;
}

int main()
{
    fin >> n >> m;
    for (int i=1; i<=m; i++)
    {
        fin >> x >> y;
        V[x].push_back(y);
        VT[y].push_back(x);
    }

    for (int i=1; i<=n; i++)
        if (!fr[i]) DFS(i);

    for (int i=n; i>=1; i--)
    {
        if (fr[Inapoi[i]])
        {
            S.push_back(vector<int>(0));
            DFST(Inapoi[i]);
        }
    }

    fout << S.size() << '\n';
    for (int i=0; i<S.size(); i++)
    {
        for (vector < int > :: iterator it = S[i].begin(); it != S[i].end(); it++)
            fout << *it << ' ';
        fout << '\n';
    }

    fout.close();
    return 0;
}